This invention relates to polymer resin systems which have been plasticized with a hydroxy substituted fatty acid containing at least about eight carbon atoms, and more particularly, polymer resins of at least one vinyl monomer and an .alpha.,.beta.-unsaturated dicarboxylic acid, anhydride or ester. The invention relates particularly to polymer resin systems based on a styrene and maleic acid or anhydride.
It is known that the flowability and processability of thermoplastic polymers can be improved by the additional thereto of various compositions which have been referred to as processing aids, internal lubricants, and/or plasticizers. The term "plasticizer" will be used in this application and in the claims to embrace processing aids and internal lubricants as well.
A critical requirement of plasticizers is that they must not deteriorate the desired physical properties of the polymer resin systems such as tensile strength, heat-distortion temperature, etc. Thus, compositions which are useful as plasticizers and some thermoplastic compositions will not be useful in other thermoplastic compositions.
Interpolymers of at least one vinyl monomer and an .alpha.,.beta.-unsaturated dicarboxylic acids, anhydrides or esters thereof are known in the art. Copolymers of styrene and maleic anhydride acid, or the esters thereof are examples of one type of interpolymer which are plasticized in accordance with this invention and which are described in the art such as in U.S. Pat. Nos. 2,430,313, 2,606,891, 2,640,819, 3,451,979 and 3,732,332.
U.S. Pat. Nos. 4,020,966 and 4,130,213 describe plastisol compositions of copolymer resins of normal alpha-olefins and maleic anhydride. These patents indicate that the plasticizer should be capable of solvating or dissolving the alpha olefin-maleic anhydride copolymer resin when heated, and they must remain essentially completely compatible with the resin upon cooling. Examples of such plasticizers given in these patents include dialkyl phthalates, alkyl phthalyl alkyl glycolates, dialkyl esters of alkane dicarboxylic acids, acetyl trialkyl citrates, and trialkyl and triaryl phosphates. Also disclosed as being useful are alkyl esters of fatty acids such as octyl stearate, epoxidized triglycerides, polyesters, amines, etc. The amount of plasticizer utilized in the resin compositions can range between about 65 to about 600 parts of the plasticizer per 100 parts by weight of the resin component.
Internal lubricants for improving the flow properties of high nitrile copolymers are described in U.S. Pat. No. 4,151,151. The lubricants are described as being polar organic materials which include phthalic anhydride, succinic anhydride, glutaric anhydride, succinimide, phthalimide, saccharin, adipamide, urea, etc.
Processing aids for nitrile resins also is the subject matter of U.S. Pat. No. 4,000,106. The processing aids are alkyl diesters of organic dicarboxylic acids. The preferred dicarboxylic acids include the propyl, butyl, amyl and hexyl phthalates, adipates, azelates, and sebecates. The processing aids are useful in the range of from about 0.05 to 2 parts by weight per 100 parts of the resin of which they are incorporated. An example in this patent indicates that stearic acid and methyl laurate were not acceptable processing aids for the particular resins studied.